A significant number of the proteins which bind to specific sites in DNA bend that DNA. Bending proteins are involved in DNA replication, transcription, and recombination, and often participate in multicomponent complexes. Their role in these complexes is probably to fix the geometry of DNA in such complexes so that all the components will interact optimally to effect the function of that complex. Thus a thorough understanding of the function of these multicomponent DNA-protein complexes will require an accurate description of their structure, including a description of the DNA path within them. Central to this description is an accurate value for the amount of bend induced by DNA bending proteins present. The research described in this application will develop a methodology which will measure the DNA bend angle induced when a protein binds to its target site. This approach measures the bend by evaluating changes in DNA topology, and can be employed with protein-DNA complexes in solution at physiological ionic strength. In addition to guantitating the amount of bend, the method can also measure the degree to which the protein binding unwinds or winds up the DNA double helix. Finally, a bacterial plasmid vector system will be developed to facilitate the analysis of any protein which bends DNA. The initial studies will characterize three transcriptional regulatory proteins: the catabolite activator protein (CAP) as well as the two oncogene products, Jun and Fos. This research characterizes fundamental interactions between DNA and proteins, and thus is important to all functions of DNA. As a result, it will contribute to a complete understanding of diseases which result from improper function of DNA, such as occurs in cancer, genetic diseases, metabolic diseases, and viral diseases.